Augmented reality (AR) refers to superimposing virtual information onto a user's sense perception, especially visual perception, so that not only information density perceived by senses may be enhanced but mental and physical efforts for switching between the real world and a display may also be saved. Since 1960, augmented reality technology has been vastly applied to surgical treatment, machine repair, military training, and even to video games. Moreover, with rapid development of portable devices, such as a mobile phone, a tablet computer or a wearable device, these devices provided with high performance processors, a variety of sensors and network connection capabilities are ideal to serve as a platform for augmented reality applications. As a result, application programs which adopt the augmented reality technology are springing up on the market, and a navigation system is one of the most important applications of the augmented reality technology.
However, the augmented reality resides technically on how to superimpose virtual information upon an image of real-world scene perceived by a user. Therefore, an augmented reality system must track and record posture information, e.g., a position and direction, of the user's head, more precisely, the eyes of the user, and use the posture information to obtain a projection transformation mapping matrix. For an outdoor navigation system, simply a Global Positioning system (GPS) module is required to obtain positioning information. In combination with posture information acquired by an inertial sensor module, the virtual information which contains guidance indication, such as a 2D word/phrase/graphic or 3D indication, may be superimposed on the image of real-world scene by virtue of the projection transformation mapping matrix for subsequent display on a screen. However, for an indoor navigation system, a GPS signal may be inaccessible. Therefore, aside from establishing an indoor GPS-like signal source, an approach of positioning in advance by means of landmarks or natural features may be adopted to facilitate correct representation of the virtual information on the image of real-world scene to be displayed. However, the aforementioned approaches require deployment of multiple positioning infrastructure, and further require establishment of a database which is used to determine the corresponding positioning information based on the positioning infrastructure, likely causing a higher deployment cost and complexity of the navigation system.